Process for recovering chips and fibers from residues of timber-derived materials, old pieces of furniture, production residues, waste and other timber containing materials

ABSTRACT

PCT No. PCT/DE95/00360 Sec. 371 Date Jan. 26, 1996 Sec. 102(e) Date Jan. 26, 1996 PCT Filed Mar. 14, 1995 PCT Pub. No. WO95/24998 PCT Pub. Date Sep. 21, 1995A process is dislcosed for recovering chips and fibers from residues of timber-derived materials, old pieces of furniture, production residues, water and other timber-containing materials glued with urea-formaldehyde binders or other binders capable of being hydrolysed or chemically disintegrated by disintegrating the timber-derived materials at a high temperature. In a first step of the process, the residues of timber-derived materials are impregnated with an impregnating solution and previously swollen until they have absorbed at least 50% of their own weight of impregnating solution. In a second step, the thus impregnated residues of timber-derived materials are heated up to 80 DEG  C. to 120 DEG  C. The thus disintegrated residues of timber-derived materials are then sorted by sieving and/or wind screening. The residues of timber-derived material have edges of at least 10 to 20 cm length. In an improved of the invention, the residues of timber derived materials are impregnated and heated at the same time.

CROSS REFERENCE TO RELATED APPLICATION

Priority is claimed to International Application Number PCT/DE95/00360having international filing date Mar. 14, 1995 and corresponding Germanpriority application No. P 44 08 788.8, filed Mar. 15, 1994.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

Not applicable

BACKGROUND OF THE INVENTION

The present invention is related to recycling systems, and in particularto a process

A known recovery process is specified in DE 42 24 629 A1. During thisprocess, the residues of derived timber products are exposed to steam athigh temperatures between 120° and 180° C. and the consequential highpressures (2-11 bar). The derived timber products are subjected to apretreatment in the course of which the material is crushed and anymetal components are removed. Chips produced according to this methodare rebonded with modified urea binders. However, the chips suffer notonly from the high temperatures but are also mechanically damaged, i.e.shortened, during the previous crushing of the starting material.Another disadvantage of this method is that it is very difficult toseparate coating materials and other undesired components from the chipsafter the steam treatment because the starting material has been sothoroughly crushed.

Another process for the recovery of chips from derived timber productsis described in DE-AS 1 201 045. This procedure involves excesspressured steam to which the residues of the derived timber products areexposed. This process is preferably performed in a steam chamber at apressure between 1 and 5 atmospheres above atmospheric pressure. Theprocess duration varies between 0.5 and 4 hours. However, the processedmaterials are not fully disintegrated, which means that subsequentcrushing is required. The chips are considerably damaged by the hightemperature and the pressure and turn brown. Chip board with acceptableproperties can only be produced of the recovered chips if fresh chipsare added. Due to the degree of damage and their brown color, it isrecommended to use the recovered chips preferably in the middle layer ofchip board.

Another method is the boiling of chip board bonded with ureaformaldehyde resins and medium density wood fiber board in largequantities of water to disintegrate them. However, this procedure isvery energy consuming and cost intensive. The increased energyconsumption is, in particular, due to the fact that such largequantities of water must be heated. The chips are boiled out, which hasa negative impact on their characteristics. The swellability of thechips is increased due to removal of timber particles, while thetechnological qualities of the chips are reduced. The binder is removedfrom the chips, which means that it cannot enhance the rebonding of therecovered chips. Additional considerable problems occurring inconnection with this method are the disposal of the produced waste waterand the drying of the soaked chips or fibers.

DE 42 01 201A1 furthermore specifies a method for the recycling ofderived timber products and wood-containing waste. This method is basedon a special mechanical treatment of the derived timber productresidues, which are subsequently processed into new semifinished orfinished products.

SUMMARY OF THE INVENTION

The purpose of the proposed invention is the introduction of anenvironmentally friendly and economically feasible method to recoverchips and fibers from derived timber products. As an additionalobjective, this method is designed to yield high-quality chip and fibermaterial (secondary chips/fibers). This

In accordance with the present invention, a process for recoveringfibers from residues of derived timber materials bonded with bindersthat can be hydrolyzed or chemically disintegrated, comprises the stepsof: impregnating the materials with a saturating or impregnatingsolution and allowing the materials to swell until the materials haveabsorbed at least 50% of their own weight in impregnating solution,thereby becoming impregnated materials; heating the impregnatedmaterials to a temperature between 80° C. and 120° C.; and separatingdisintegrated material from other components by one or more techniquesselected from the group consisting of sieving and wind screening.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be more fully understood in view of the followingDetailed Description of the Invention, and the Drawing, of which:

FIG. 1 is a block diagram which illustrates a plant for disintegratingchip board and residues of wood-containing materials; and

FIG. 2 is a flow diagram which illustrates stages for the process ofFIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In the first step of the process the derived timber products areimpregnated with an impregnating solution or saturant and allowed toswell until they have absorbed at least 50% of their own weight inimpregnating solution. In the second step the impregnated derived timberproducts are heated to 80°-120° C. until the bonding between the fibersand chips is dissolved due to the influence of the impregnating solutionand the high temperature. This means that the bonding is chemicallydissolved by hydrolysis and mechanically destroyed by swelling. Theamount of impregnating solution absorbed by the derived timber productsand the impregnation process are adjusted in such a way that the derivedtimber products are fully dissolved in the specified temperature rangeand that the entire liquid is absorbed during the disintegration processso that no surplus solution remains to be disposed of. The proposedmethod consists of a combination of chemical, thermal and mechanicalprocesses. These processes allow disintegration of derived timberproducts at relatively harmless disintegration parameters and ensurethat the chips or fibers will not be damaged but may even be upgradedduring recovery. This is possible because the material is impregnated orsaturated with the impregnating solution in such a way that no boilingsolution or waste water remains to be disposed of after thedisintegration process. The impregnating solution allows full hydrolysisalready at a minimum temperature of 80° C., though the optimum operatingtemperature is 80°-120° C. The low temperatures ensure that thegeometrical properties of the chips and fibers remain unchanged. Thechemical and physical properties of the fibers and chips are notaffected or even improved by the disintegration process. Secondary chipsand secondary fibers can be produced with modest financial expenditureand technical requirements and can be used in conventional processingplants to produce new derived timber products such as chip board andwood fiber board with and without the addition of fresh fibers or freshchips, respectively. The thus created derived timber products have equalor even better properties than derived timber products made of freshmaterial. This applies to both the technological properties and theemission of formaldehyde. Secondary fibers and chips can be bonded withconventional binders. The consumption of binders is not increased butcan, on the contrary, even be reduced through the proposed method.

The actual recovery begins with the addition of the impregnatingsolution to the derived timber products. The quantity of impregnatingsolution must be calculated in such a way that the derived timberproducts will have absorbed at least 50% of their own weight inimpregnating solution when the last of the solution is gone. It isimportant to stir the derived timber products in the container so thatthe added solution is evenly absorbed. Even absorption can be enhancedby a rotating container. As an alternative method, it is possible to addan excess quantity of impregnating solution so that the wood-containingmaterial is fully submerged in the liquid. The surplus amount of liquidcan be drained when the pieces of timber have absorbed at least 50% oftheir own weight in liquid. The drained liquid need not be discarded butcan be used to disintegrate further batches of derived timber products.Saturated with impregnating solution, the derived timber products aretransferred from the impregnation container into a disintegration boilerwhere they are heated to a temperature of between 80° and 120° C. Theinfluence of the temperature and the effect of the impregnating solutioncause hydrolytic disintegration of the bonding. As a different variationof the same method it is proposed that the impregnation process need notnecessarily take place in an individual container and that it ispossible, instead, to use the disintegration as an impregnationcontainer in which the starting material is first impregnated. Then thetemperature is raised as soon as the liquid has been fully absorbed bythe derived timber products or the surplus impregnating solution hasbeen drained. The temperature increase can take place either underpressure (i.e. in the pressure sealed disintegration boiler) or underabmbient atmospheric conditions. The level of the pressure depends onthe selected temperature.

The duration of the disintegration phase depends on the previousimpregnation, the composition of the impregnating solution, thetemperature and the heating time of the disintegration boiler and variesbetween 1 and 60 minutes. The disintegration process will be acceleratedby higher temperatures, a higher proportion of impregnating solution anda higher acid content in the impregnating solution, while lowertemperatures, a smaller amount of impregnating solution and a basicimpregnating solution will slow it down.

The initial pressure level during the heating process is at ambientatmospheric The maximum pressure should not exceed 2 bar excess pressureto ensure gentle disintegration. For gentle but nevertheless fastdisintegration it is recommended to choose a temperature not exceeding120° C.

To accelerate the impregnation process it is recommended to evacuate theimpregnation container (underpressure) or to increase the pressure inthe impregnation container beyond normal. Vacuum treatment (i.e.underpressure of e.g. 150 mbar (absolute) in the impregnation container) causes the air contained in the derived timber products to evaporate.Under normal pressure, this air prevents penetration by the impregnatingsolution and would render disintegration of coated derived timberproducts with large surfaces virtually impossible without underpressure.Air-filled cavities account for approximately 30-70 % of the totalvolume of the derived timber products. Excess pressure can alsofacilitate the penetration of the derived timber products by theimpregnating solution. It is also possible to speed up the impregnationprocess by a combination of excess pressure and underpressure. The sameeffect can be achieved by heating the impregnating solution or thederived timber products before or during the impregnation process.Thereby, the heat emitted by the exhaust gases of the disintegrationboiler or during discharging of the disintegrated material can be usedfor energy-saving heating of the impregnating solution. The heat emittedby the exhaust gases of the disintegration boiler or during dischargingor sorting of the disintegrated material can also be used to heat thematerial to be disintegrated.

Another variation of the same method involves a rotating disintegrationboiler or a disintegration boiler with a stirring device in which thederived timber products are mixed with the impregnating solution.(Thereby, the amount of impregnating solution to be added must becalculated in such a way that no impregnating solution or waste lye willbe left in the container for disposal after the disintegration process).The disintegration boiler is heated to a temperature of 80°-120° C. Inthis process the mechanical destruction of the bonding by swelling andthe chemical dissolution by hydrolysis take place simultaneously. Thismeans that the derived timber products are simultaneously exposed to theimpregnating solution and the temperature (and the respective pressure).

The impregnating solution allows disintegration at low temperatures withand without pressure. This means that the chips and fibers are treatedvery gently and that the binders contained in the waste materials (e.g.urea) are not damaged or only slightly damaged and can enhance therebonding process or even be reactivated (i.e. reduction of binderconsumption and formaldehyde emission). At the same time it is possibleto avoid the undesired emissions characteristic of work at highertemperatures and pressures.

After the disintegration process the derived timber products arecompletely dissolved. The chips and fibers, the coating materials, thesolid timber components, the edge veneers, any metal components and anyother components are separated from the chip or fiber material and canbe sorted by sieving, wind screening, a combination of sieving and windscreening or any new separating method. It is particularly easy toremove the wood chips and fibers, because the fibers and chips are muchsmaller than, for example, the coating materials that have notdisintegrated but retained the size of the crushed derived timberproducts originally fed into the boiler.

The water content of the chips and fibers after the disintegrationprocess corresponds to that of fresh timber or is even lower. Theincreased temperature of the chips after the disintegration facilitatestheir drying. The recovered chips can either be dried separately in theconventional method or together with fresh chips or wood fibers. Therecovered chips and fibers can be processed into chip and wood fiberboard with unmodified commercial binders and without addition of freshchips and fibers. The thus produced chip board or wood fiber board hasequal or even better properties than the starting material. This appliesto both the technical properties and formaldehyde emission.

Particularly fast and full disintegration can be ensured by allowing thederived timber products to absorb 80% of their own weight inimpregnating solution. The absorption of the impregnating solution cantake place at normal temperature (ambient temperature) and normalpressure. The absorption can be accelerated by vacuum treatmentpreceding the impregnation, by alternating pressure treatment, byheating of the impregnating solution, by heating of the material to bedisintegrated or by any combination of the above possibilities.

The recommended size of the derived timber products to be disintegratedis 10-20 cm (average edge length). The derived timber products can becrushed to the required size by means of a slowly rotating commercialcrusher. The recommended size ensures that the fibers and chips will notbe severely damaged. This applies even to the chips and fibers locatedalong the edges of the boards, because the special, slow roller of thecrusher does not usually crush the chips or fibers but usually breaksentire fibers or chips out of the bonding substance. Coating materialsand other undesired materials in the chip or fiber material largelyretain their original size because they are not disintegrated and can,therefore, easily be separated after disintegration. Such large piecesof derived timber products can be used because the impregnatingtreatment ensures that the starting material is saturated withimpregnating solution so that the binder can be destroyed throughout bychemical and hydrolytic effects enhanced by heat.

The impregnating solution offers numerous possibilities to control thedisintegration process and, in particular, the result of thedisintegration process. It is, for instance, possible to modify thecomposition of the disintegration solution in such a way that thequality of the chips and fibers is even improved during thedisintegration process. This means that particular impregnating and/ordisintegrating conditions can ensure that the chemical and physicalproperties of the recovered chips will be better than those of freshchips. Chip board and medium density wood fiber board made of oldfurniture are marked by relatively high formaldehyde emissions andcontents. Therefore, it can definitely be recommended to supplement theimpregnating solution by formaldehyde-binding, formaldehyde-inhibitingor formaldehyde-destroying chemicals such as urea or ammonia or withchemicals that can separate urea or ammonia. Thus, it is possible toreduce the formaldehyde concentration in or eliminate formaldehydealtogether from the exhaust air and drying air after the disintegrationprocess. Basic substances can be added to counteract the formation ofacids. Acids contained in the wood can be neutralized. The chips can,for instance, be adjusted to a slightly basic level. Thus, it ispossible to delay the hardening of added binders, which is aparticularly interesting option in the case of long intervals betweenthe application of the binder and the actual pressing of the boards. Itis, furthermore, possible to apply coatings that require a basic groundto derived timber products of secondary fibers or secondary chips. Acidscan be added, on the other hand, to increase the acidity of therecovered chips and fibers. This means that less or no hardeners must beadded to the binder or that the hardening of the, binder will beaccelerated. The addition of acids is also recommended if the recoveredchips and fibers are to be used for the production of materials thatwill be treated with coatings based on -acid-hardening adhesive systems.In such cases it would be possible to simplify the adhesive system andthe application of the coating would be accelerated as well. Theaddition of acids to the impregnating solution would also accelerate thedisintegration process. Another positive option is the addition ofoxidizing agents or reducing agents. Such agents can, on the one hand,serve to destroy emitted formaldehyde. On the other hand, the additionof peroxides can, to a certain degree, reactivate urea. Anotherrecommendable option in terms of the composition of the impregnatingsolution is the addition of binders such as urea formaldehyde resins orbinder additives such as paraffines. This will reduce the amount offormaldehyde emission and have a positive influence on the subsequentswelling and water absorption characteristics of the secondary chips andfibers. Additional bonding of the recovered chips and fibers can bereduced or will not be required at all. The chips and fibers need not becompletely dried for further processing. If the recovered chips are tobe split up into fibers for wood fiber board production it isrecommended to add lignin-softening chemicals such as methanol,sulphites or ammonia in order to save energy during the subsequent fiberproduction.

The standard impregnating solution contains approximately 0.5-3% ureaand approximately 0.1-1% ammonia or approximately 0.5% soda lye(dissolved in water). The chemicals contained in the impregnatingsolution do not cause delignification as in pulp production.

The disintegration process can be positively influenced by the additionof chemicals to the mass in the disintegration boiler during thedisintegration process. It is, for instance, possible to add ozone inorder to destroy the emitted formaldehyde.

As high temperatures damage the chips, it is recommended to base thedisintegration process on a controlled temperature scheme. Thetemperature can, for instance, be increased to a higher level at thebeginning and reduced toward the end of the disintegration process.Other non-constant temperature schemes are also possible. The proposedprocedure is described in greater detail by means of the followingexamples 1-11:

EXAMPLE 1

Old furniture, production residues and spoilage containing chip boardand/or medium density wood fiber board or other wood-containingmaterials are crushed into pieces (edge length approx. 10-20 cm) bymeans of a commercial crusher (e.g. crushers by Pailmann or Maier).Crushing to the above size ensures on the one hand optimum piled weight(mass per volume). On the other hand, the chips and fibers as well asthe coating materials and edge veneers do not suffer significantmechanical damage. Components of metal, plastic or solid wood need notbe removed. Chip board and medium density wood fiber board as well asother wood-containing materials can be disintegrated together orseparately. The crushed pieces are filled into a static or rotatingdisintegration boiler/pressure vessel. The recommended dimensions yielda piled weight of approximately 350-400 kg/m3. The pressure vessel isclosed and evacuated so that the pressure in the container is reduced toan underpressure of 150-200 mbar (absolute). The time needed to createthis underpressure depends on the respective technology. The aircontained in the wood-containing materials escapes and the addedimpregnating solution can penetrate the materials very quickly. The timerequired for full penetration varies between 5 and 15 minutes for chipboard and depends on the type of derived timber product, theunderpressure and the composition and temperature of the impregnatingsolution. The impregnating solution consists of water, urea and sodalye. The wood-containing material is exposed to this solution until ithas absorbed at least 50% of its own weight. The required bath ratio(i.e. the ratio between wood-containing material and impregnatingsolution after completion of the impregnation process) is 1:0.5. Then,the pressure in the disintegrating boiler is restored to normal and theremaining impregnating solution is drained from the container. Thedrained solution can be used for the next disintegration process. Then,the disintegrating container is closed again and heated to a temperatureof 110° C. for approximately 20 minutes. The container will heat up veryquickly because of the open spaces between the board pieces. After thistreatment the chips and fibers can be retrieved in their originalgeometrical shape. The coating materials and edge veneers as well as anyother undesired materials have been separated from the chips and fibersand can be removed by sieving or wind screening or a combination ofboth. The same applies to solid timber components or pieces of chipboard or wood fiber board that have remained whole. The residues can besubjected to further sorting (e.g. solid timber, plastic, metal etc.).These materials can be recycled, used to generate thermal energy orpower or be disposed of. Metals can, for instance, be removed by meansof magnets or metal detectors. Plastic and solid timber components canbe identified and separated by NIR spectroscopy or other methods.

The recovered chips and fibers can be processed into chip board or woodfiber board without addition of fresh chips or fibers, usingconventional technologies and unmodified commercial binders such as ureaformaldehyde resins, melamine formaldehyde resins, phenol formaldehyderesins, isocyanates (MDI/PMDI) or mixed resins. The produced board willhave equal or even better properties than the starting material (seetables 1 and 2). This applies to both the technological properties andformaldehyde emission values.

EXAMPLE 2

Procedure as in example 1. Difference: The starting material and theimpregnating solution are mixed in the desired bath ratio and filledinto a rotating disintegrating boiler or one with an integrated stirringdevice. This means that the amount of impregnating solution added mustcorrespond to the absorption capacity of the material to be processed.Mixing and even absorption of the impregnating solution is ensured bythe rotation of the disintegration container or the stirring device,respectively. The disintegrating container can be heated right from thebeginning, i.e. the heat can be turned on as soon as the container isclosed.

EXAMPLE 3

Procedure as in example 1. Difference: The impregnation process and thedisintegration process take place in separate containers. Theimpregnated pieces of wood-containing material are transferred from theimpregnation container into the disintegration boiler, which means thata direct heat increase is possible.

EXAMPLE 4

Procedure as in example 1. Difference: no underpressure.

EXAMPLE 5

Procedure as in examples 1, 2, 3 and 4. Difference: Disintegration takesplace without pressure.

EXAMPLE 6

Procedure as in examples 1 and 4. Difference: The temperature of theimpregnating solution is higher than the ambient temperature.Recommended temperature: 60°14 80° C.

EXAMPLE 7

Procedure as in examples 1, 2 and 4. Difference: Impregnation anddisintegration take place continuously (or "batch" production).

EXAMPLE 8

Procedure as in examples 1, 2, 3 and 4. Difference:Formaldehyde-binding, formaldehyde-inhibiting or formaldehyde-destroyingchemicals such as urea or ammonia or substances separating urea orammonia are added to the impregnating solution.

EXAMPLE 9

Procedure as described in examples 1, 2, 3 and 4. Difference: Lyes suchas soda lye, acids such as sulphuric acid, oxidizing or reductionagents, binders such as urea formaldehyde resins or substancespreserving or reactivating the existing binders are added to theimpregnating solution. Maximum total concentration of all chemicals:30%.

EXAMPLE 10

Procedure as described in examples 1, 2, 3 and 4. Difference: Therecovered chips or fibers are treated with the chemicals mentioned inexamples 8 and 9 after the disintegration process while they are eitherstill wet, slightly dried or after complete drying.

EXAMPLE 11

Procedure as described above. Difference: The chemicals mentioned inexamples 8 and 9 or other chemicals are added to the material in thedisintegration boiler during the disintegration process. It is, forinstance, possible to add ozone to destroy formaldehyde emitted by thedisintegrating material.

EXAMPLE 12

Procedure as described above. Difference: Two or more disintegrationboilers are combined into one large production unit and operatedsimultaneously.

Tables 1 and 2 illustrate the characteristics of board produced ofrecovered chips.

Table 1: Characteristics of a laboratory chip board produced ofrecovered chips, characteristics of the furniture chip board (year ofproduction: 1993) from which the chips were recovered (after removal ofthe coating material) and characteristics of a laboratory chip boardmanufactured of industrial chips supplied by the manufacturer of thefurniture chip board.

Table 2: Characteristics of a laboratory chip board produced ofrecovered chips (secondary chips), characteristics of the old furniturechip board (year of production: 1964) from which the chips wererecovered (after removal of the coating material) and characteristics ofa laboratory medium density fiber board manufactured of fibers producedby grinding the chips recovered from the old furniture chip board.

The process is explained by means of an example.

FIG. 1 illustrates a plant for the disintegration of chip board andresidues of wood-containing materials according to the proposed method.FIG. 2 illustrates the stages of the process.

The wood-containing material is transferred into a crusher (2) by meansof a wheel loader (1), a grab excavator or any other adequate equipment.The crusher (2) crushes the wood-containing material into flat pieces(average edge length 10-20 cm). The crushed material is then conveyedinto the disintegration boiler (3) by means of adequate conveyingequipment (17). In the illustrated model, the disintegration boiler (3)also serves as the impregnation container. The filled disintegrationcontainer (3) is locked airtight. A vacuum pump (9) is used to suck offthe air contained in the disintegration boiler (3) and thewood-containing material until an absolute underpressure of 150-200 mbaris reached. Still under vacuum, the disintegration boiler (3) is filledwith impregnating solution from the impregnating solution tank (4) via apipe (15) until the wood-containing material is fully submerged inimpregnating solution. Then the pressure in the disintegration boiler(3) is restored to normal. It would also be possible to use overpressureto accelerate the impregnation process. The impregnating solution tank(4) contains a stirring device (5) as well as supply pipes for chemicals(6) and water (7). After the impregnation process, i.e. when thewood-containing material has absorbed at least 50% of its weight inimpregnating solution, the remaining solution from the disintegrationboiler (3) back into the impregnating solution tank (4) via a pipe (10)provided for that purpose. From there, the drained impregnating solutionis later retransferred into the disintegration boiler for the nextimpregnation process together with the new solution mixed for thatpurpose. After draining, the disintegration boiler (3) is once againhermetically closed. Then, it is heated either via the outer surface orthrough direct heat. The heat from the heat source (8) is therebytransferred to the boiler by means of hot air, steam of any othergaseous heat transfer medium. The disintegration boiler (3) is, forexample, heated to a temperature of 110° C. for a period of 20 minutes.Then, the heat source is switched off and the disintegration boiler (3)is emptied by means of an unloading device (16). The disintegrationboiler could also be emptied via an opening that extends over the entirewidth of the bottom section of the boiler. The disintegrated material isconducted into a silo (11) or into any other suitable storage container.From there, it is continually fed into a sieving machine (12). There,the chips and fibers are separated from coating materials, solid wood,edge veneers and other undesired components. The removed chips or fibersare then transferred to the reprocessing plant (14). The othercomponents can either be sorted or compressed in a press (13) to reducetheir volume.

                  TABLE 1                                                         ______________________________________                                                      Furniture                                                                            Laboratory                                                                              Laboratory                                                   chip board                                                                           chip board                                                                              chip board                                                   without                                                                              of secondary                                                                            of fresh                                                     coating                                                                              chips     chips                                                        19 mm  19 mm     19 mm                                          ______________________________________                                        Bulk density  g/cm.sup.3 !                                                                    0.703    0.674     0.673                                      Module of elasticity  N/mm2!                                                                  2410     2460      2600                                       Flexural strength  N/mm2!                                                                     11.99    12.55     15.20                                      Transverse pull resistance                                                                    0.529    0.520     0.668                                       N/mm2!                                                                       Delamination strength  N/mm2!                                                                 1.10     1.17      1.27                                       Shear resistance  N/mm2!                                                                      1.71     1.48      1.70                                       Perforator values  mg/100 g!                                                                  6,8      5.4       8.1                                        Humidity at 20/65  %!                                                                         10.0     9.5       10.1                                       ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                    Old furniture                                                                          Laboratory                                                                              Laboratory                                                 chip board                                                                             chip board                                                                              medium                                                     (1964), without                                                                        of secondary                                                                            density fiber                                              coating  chips     board                                                      19 mm    19 mm     19 mm                                          ______________________________________                                        Bulk density  g/cm.sup.3 !                                                                  0.621      0.712     0.760                                      Module of elasticity                                                                        3020       3730      3530                                        N/mm2!                                                                       Flexural strength  N/mm2!                                                                   18.11      23.63     23.20                                      Transverse pull resistance                                                                  0.30       0.34      0.53                                        N/mm2!                                                                       Delamination strength                                                                       1.05       1.20      1.30                                        N/mm2!                                                                       Shear resistance  N/mm2!                                                                    1.21       1.33      1.77                                       Perforator values                                                                           14.6       9.5       2.0                                         mg/100 g!                                                                    Humidity at 20/65  %!                                                                       10.27      9.77      8.06                                       ______________________________________                                    

What is claimed is:
 1. A process for recovering particles from residues of derived timber materials bonded with binders that can be hydrolyzed or chemically disintegrated, comprising the steps of:impregnating the materials with an impregnating solution and allowing the materials to swell until the materials have absorbed at least 50% of their own weight in impregnating solution, thereby becoming impregnated materials; heating the impregnated materials to a temperature between 80° C. and 120° C.; and separating disintegrated material from other components by one or more techniques selected from the group consisting of sieving and wind screening.
 2. The process according to claim 1, wherein said impregnating step and said disintegrating step take place in two separate containers, the impregnated material being heated in a disintegration boiler.
 3. The process according to claim 2, wherein the impregnating container is a rotating container, the rotating action of which ensures proper mixing of the of the wood-containing material and the impregnating solution.
 4. The process according to claim 2, wherein the impregnating container is equipped with a mixing device to ensure proper mixing of the of the wood-containing material and the impregnating solution.
 5. The process according to claim 2, wherein the disintegration container is a rotating container.
 6. The process according to claim 2, wherein the disintegration container is equipped with a mixing device.
 7. The process according to claim 1, wherein said impregnating and heating steps both take place in a disintegration boiler.
 8. The process according to claim 7, wherein said impregnating step takes place before the disintegration boiler is heated.
 9. The process according to the claim 7, wherein said impregnating and heating steps take place simultaneously.
 10. The process according to claim 1, wherein the derived timber materials subjected to said impregnating step are substantially flat and have an edge length of approximately 10-20 cm.
 11. The process according to claim 1, wherein said impregnating step lasts at least 1 minute.
 12. The process according to claim 1, wherein the material is exposed to an increased temperature for a least 1 minute.
 13. The process according to claim 1, wherein an amount of impregnating solution calculated to be entirely absorbed is added to the wood-containing material.
 14. The process according to claim 1, wherein an amount of impregnating solution calculated to entirely submerge the material is added to the wood-containing material in a container, any surplus amount of impregnating solution being drained from the container after the impregnating step.
 15. The process according to claim 14, wherein entire process takes place in a static container.
 16. The process according to claim 1, wherein a disintegrating container is employed and a pressure in the disintegrating container is raised to an overpressure of up to 2 bar.
 17. The process according to claim 1, wherein the wood-containing materials contain a proportion of the impregnating solution corresponding to 80% of their own weight, and the materials are exposed to a temperature of 110° C. for 20 minutes.
 18. The process according to claim 1, wherein increased temperature is allowed to take effect at ambient atmospheric pressure.
 19. The process according to claim 1, wherein impregnating with the impregnating solution takes place at an underpressure below ambient atmospheric pressure.
 20. The process according to claim 1, wherein impregnating with the impregnating solution takes place at excess pressure above ambient atmospheric pressure.
 21. The process according to claim 1, wherein impregnating with the impregnating solution takes place at a combination of underpressure and excess pressure applied at different respective times.
 22. The process according to claim 1, wherein the wood-containing material is heated before the impregnating step.
 23. The process according to claim 1, wherein the impregnating solution is heated during and before the impregnation process.
 24. The process according to claim 1, wherein the impregnating solution is supplemented by one or more substances selected from the group consisting of: formaldehyde-binding chemicals, formaldehyde-inhibiting chemicals, formaldehyde-destroying chemicals, urea, ammonia, chemicals that can separate urea, and chemicals that can separate ammonia.
 25. The process according to claim 1, wherein the impregnating solution is supplemented by one or more chemicals selected from the group consisting of: lyes, acids, oxidation agents, reduction agents, binders, urea formaldehyde resins, substances preserving existing binders, and substances reactivating existing binders, maximum total concentration of all chemicals: 30%.
 26. The process according to claim 25, wherein the chemicals are added in a disintegration container during a disintegration process.
 27. The process according to claim 1, wherein a predetermined temperature scheme including heating to a temperature of up to 120° C. is used during the heating step.
 28. The process according to claim 1, wherein recovered particles are treated with one or more chemicals selected from the group consisting of: formaldehyde-binding chemicals, formaldehyde-inhibiting chemicals, formaldehyde-destroying chemicals, urea, ammonia, chemicals that can separate urea, chemicals that can separate ammonia, lyes, soda lye, acids, sulphuric acid, oxidation agents, reduction agents, binders, urea formaldehyde resins, substances preserving existing binders, and substances reactivating the existing binders after the disintegration process.
 29. The process according to claim 1, wherein impregnating with the impregnating solution takes place after an under pressure treatment (evacuation) of the wood-containing material relative to ambient atmosphere pressure.
 30. The process according to claim 1, wherein the impregnating solution is heated during the impregnation process.
 31. The process according to claim 1, wherein the impregnating solution is heated before the impregnation process.
 32. A process for recovering particles from residues of derived timber materials, comprising the steps of:impregnating the materials for at least one minute with an amount of impregnating solution calculated to submerge the materials, said impregnating step including allowing the materials to swell in a container while being mixed until the materials have absorbed at least 50% of their own weight in impregnating solution, said materials thereby becoming impregnated materials; heating the impregnated materials to a temperature between 80° C. and 120° C.; and separating disintegrated material from other components.
 33. The process of claim 32, wherein different containers are used for said impregnating step and said heating step.
 34. The process of claim 33, wherein said impregnating step takes place at an underpressure below ambient atmospheric pressure.
 35. The process of claim 33, wherein said impregnating step takes place at excess pressure above ambient atmospheric pressure.
 36. The process of claim 33, wherein said impregnating step takes place at a combination of underpressure and excess pressure at different respective times.
 37. The process of claim 33, wherein said impregnating solution is supplemented by one or more chemicals selected from the group consisting of: formaldehyde-binding chemicals, formaldehyde-inhibiting chemicals, formaldehyde-destroying chemicals, urea, ammonia, chemicals that can separate urea, chemicals that can separate ammonia, lyes, acids, oxidation agents, reduction agents, binders, substances that preserve existing binders, and substances that reactivate existing binders. 